Ke Yang's research while affiliated with China University of Geosciences (Beijing) and other places

The Solonker suture zone is one of the most important tectonic boundaries in the southeastern part of the Central Asian Orogenic Belt (CAOB). An ~ 630 km-long reflection seismic profile across this suture was recently completed by the Chinese SinoProbe Project. The processed seismic data show clear crustal structures and provide new constraints on the tectonic and crustal evolution models. The Moho is delineated as a relatively flat boundary between a strongly reflective lower crust and a transparent mantle at a depth of ~ 40–45 km (~ 14.5 s two-way travel time), which is in agreement with the refraction data recorded along the same profile. In a broad view, the profile images an orogen that appears bivergent with, and approximately centered on, the Solonker suture zone. The southern portion of this profile is dominated by a crustal-scale, cratonward propagating fold-and-thrust system that formed during the late Permian and Triassic through collision and subsequent convergence in a post-collisional stage. The major thrust faults are truncated by Mesozoic granitoid plutons in the upper crust and by the Moho at the base of the crust. This geometry suggests that the Moho was formed after the thrusting event. The northern portion of the profile, although partially obliterated by post-collisional magmatic bodies, shows major south-dipping folding and thrusting. Bands of layered reflectors immediately overlying the Moho are interpreted as basaltic sills derived from the mantle. Episodic mafic underplating may have occurred in this region, giving rise to post-collisional magmatic events and renewal of the Moho. A few mantle reflectors are also visible. The overall geometry of these mantle reflectors supports the tectonic models that the southern orogen (Manchurides) experienced south-directed subduction and the northern orogen (Altaids) underwent north-directed subduction prior to collision along the Solonker suture zone.

The newly-discovered Shiyaogou molybdenum deposit is located in the eastern Qinling metallogenic belt in central China. The deposit contains at least 152,000 t of Mo metal and bears typical porphyry-type features in terms of its concentric alteration zonation, quartz vein-hosted Mo mineralization, veining sequence and the spatial association with concealed granite porphyries. Re-Os isotope analyses of molybdenite from the deposit yield an ore-forming age of 132.3 +/- 2.8 Ma. LA-ICP-MS U-Pb zircon dating of ore-related porphyries yields crystallization ages from 135 Ma to 132 Ma, indicating a temporal link between granitic magmatism and Mo mineralization. A population of captured magmatic zircons indicates another pulse of magmatism at similar to 143 Ma. A barren granite intrusion near the deposit gives a zircon U-Pb age of 148.1 +/- 1.1 Ma. These magmatic activities were concurrent with the emplacement of the nearby Heyu granitic batholith, a largely ore-barren intrusive complex formed from similar to 148 Ma to similar to 127 Ma. Zircon Ce4+/Ce3+ ratios of ore-related porphyries are obviously higher than those of contemporaneous barren granitoids, implying an affinity between Mo mineralization and highly oxidized magmas. Moreover, zircons from these granitoids overall have decreasing Ce4+/Ce3+ ratios from 148 Ma to 132 Ma, reflecting decreasing oxygen fugacities during magma evolution. Available geological, radiometric and stable isotopic evidence suggests that the decrease of magma oxygen fugacity was probably associated with an increase of mantle contribution to granitic magmatism and metallogenesis, which probably gave rise to successive mineralization of Mo and Au in the eastern Qinling. The intense magmatic-metallogenic events in the eastern Qinling during Late Jurassic to Early Cretaceous times are interpreted as a response to the large-scale lithosphere thinning and subsequent asthenosphere upwelling beneath the eastern part of the North China Craton.